Question

Which of the following has the same molecular formula and empirical formula?
(A) $ C{O_2} $
(B) $ {C_6}{H_3}{O_6} $
(C) $ {C_2}{H_4} $
(D) $ {C_2}{H_6} $

Answer 1

Hint: To answer this question we have to know about molecular formulas and empirical formulas. The molecular formula is the chemical formula which tells the total number of atoms of each element which is in the molecule of the substance whereas the empirical formula indicates the simplest positive integer ratio of the atoms which are in the compound.

Complete Step By Step Answer:
The molecular formula is the formula which is the number of atoms present in each element in the single molecule of the compound. In other words, it is the formula that shows the actual number of each atom present in the molecule. If we know the value of molar mass then the molecular formula can be calculated by using an empirical formula.
Empirical formula is the simplest type of notation. Empirical formulas are the same as molecular formulas and can express the variety of different chemical isomers or compositions. The molecular formula is similar to the empirical formula or the whole-number multiple.
Here, in the question the molecular and empirical formula of the four compounds are:

Compound	Molecular Formula	Empirical Formula
$ C{O_2} $	$ C{O_2} $	$ C{O_2} $
$ {C_6}{H_3}{O_6} $	$ {C_6}{H_3}{O_6} $	$ {C_2}H{O_2} $
$ {C_2}{H_4} $	$ {C_2}{H_4} $	$ C{H_2} $
$ {C_2}{H_6} $	$ {C_2}{H_6} $	$ C{H_3} $

Thus, from this table we can see here $ C{O_2} $ has the same molecular formula and empirical formula.
So, option $ \left( A \right) $ is correct.

Note:
The empirical formula is used to show what elements are there in the molecule. The empirical formula is very much useful when we want to find at a glance what elements we are dealing with. On the other hand, a molecular formula is to know the number of atoms of the elements in the compound.